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Discovery
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| Discovered by | Albert George Wilson, Rudolph Minkowski |
| Discovery date | September 14, 1951 |
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Designations
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| Named after | National Geographic Society |
| Alternate name(s) | 1951 RA |
| Minor planet category |
Apollo, Mars-crosser |
| Epoch March 6, 2006 (JD 2453800.5) | |
| Aphelion | 248.810 Gm (1.663 AU) |
| Perihelion | 123.817 Gm (0.828 AU) |
| Semi-major axis | 186.314 Gm (1.245 AU) |
| Eccentricity | 0.335 |
| Orbital period | 507.665 d (1.39 a) |
| Average orbital speed | 25.92 km/s |
| Mean anomaly | 147.839° |
| Inclination | 13.341° |
| Longitude of ascending node | 337.293° |
| Argument of perihelion | 276.793° |
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Physical characteristics
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| Dimensions | 5.1×1.8 km[1] |
| Mass | ~2.6×1013 kg |
| Mean density | 2.0? g/cm³ |
| Equatorial surface gravity | ~0.0008 m/s² |
| Escape velocity | ~0.0015 km/s |
| Rotation period | 0.217 d (5.223 h)[1] |
| Albedo | 0.325[1] |
| Temperature | ~249 K |
| Spectral type | S[1] |
| Absolute magnitude (H) | 15.60[1] |
The asteroid 1620 Geographos ( /dʒiːoʊˈɡræfɒs/) was discovered on September 14, 1951 at the Palomar Observatory by Albert George Wilson and Rudolph Minkowski. It was originally given the provisional designation 1951 RA. Its name, a Greek word meaning "geographer" (geo– 'Earth' + graphos 'drawer/writer'), was chosen to honour geographers and the National Geographic Society.
Geographos is a Mars-crosser asteroid and a near-Earth object belonging to the Apollos. In 1994, during the asteroid's closest approach to Earth in two centuries at 5.0 Gm-which will not be bettered until 2586- a radar study of it was conducted by the Deep Space Network at Goldstone, California. The resultant images show Geographos to be the most elongated object in the solar system; it measures 5.1×1.8 km.
Geographos is an S-type asteroid, meaning that it is highly reflective and composed of nickel-iron mixed with iron- and magnesium-silicates.
Geographos was to be explored by the U.S.'s Clementine mission; however, a malfunctioning thruster ended the mission before it could approach the asteroid.
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